This ‘comet’ is acting so weird, scientists are asking if it’s alien
How did your country report this? Share your view in the comments.
Diverging Reports Breakdown
Astronomers discover 7 new ‘dark comets,’ but what exactly are they?
Scientists have discovered seven more “dark comets” Analysis of this haul suggests that the puzzling planetoids are divided into two distinct families. One type lurks in the outer solar system, in the realm of the gas and ice giants . The other group is located in the inner solar system. The outer dark comets are larger, with diameters hundreds of meters across or less. The inner dark comet have more elliptical orbits that are more like those of the typical comets, whereas the inner comets have more circular orbits like those in the solar system’s inner planets.. How these mysterious comets came to be in these locations at the summer of 2024, however, remains a mystery. The discovery of the first “dark comet” in 2023 led to the use of the term ‘dark comet’ for the first time. In the sense that these bodies act like a comet but don’t light up like a Comet — though they are still visible as points of light through a powerful telescope. They are known as active asteroids, which are comet-like objects.
Of late, the dividing line between asteroids and comets has become blurred. There are ” main-belt comets ,” also known as active asteroids, which are comet-like objects possessing the properties of asteroids. Then there are dark comets, which are the opposite: asteroids that have some of the characteristics of comets.
As their name suggests, main-belt comets tend to inhabit the main asteroid belt between Mars and Jupiter . But they grow tails just like a comet, whereas dark comets have no tails but move like a comet, in the sense that they display non-gravitational acceleration. In other words, some other force besides gravity is acting on their motion, changing their trajectory. For a regular comet, this other force is the thrust produced by ices sublimating into vapor on their surface when they near the heat of the sun and outgas into space, carrying the dust that produces their iconic tails. Yet dark comets have no tails.
“When you see that kind of perturbation on a celestial object, it usually means it’s a comet, with volatile material outgassing from its surface giving it a little thrust,” Davide Farnocchia, of NASA’s Jet Propulsion Laboratory in Southern California, said in a statement . “But try as we might, we couldn’t find any signs of a comet’s tail.”
Related: Comets: Everything you need to know about the ‘dirty snowballs’ of space
We’ve seen this mysterious motion before. In 2017, the interstellar object 1I/’Oumuamua sped through the inner solar system before heading back toward interstellar space. As it did so, its trajectory altered from that which gravity alone had planned for it — ‘Oumuamua seemed to be getting an extra push from somewhere.
Although no tails or outgassing were detected coming from ‘Oumuamua, causing its mystery to linger, ‘Oumuamua’s behavior bore a remarkable resemblance to another object found to be acting strangely just a year earlier.
Get the Space.com Newsletter Breaking space news, the latest updates on rocket launches, skywatching events and more! Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors
That object, known as 2003 RM, had been thought to be just another asteroid, until it too was noticed to be moving under a non-gravitational force.
“The fact that the first object we discovered from interstellar space exhibited similar behaviors to 2003 RM made 2003 RM even more intriguing,” said Farnocchia.
By 2023, six other similar objects had been discovered, and the term “dark comet” was used for the first time, in the sense that these bodies act like a comet but don’t light up like a comet — though they are still visible as points of light through a powerful telescope. The assumption is that dark comets are outgassing, but on a barely perceptible level, just enough to give them a push.
Now, another seven dark comets have been identified, bringing the tally to 14 — enough to start drawing some conclusions about their properties.
“We had a big enough number of dark comets that we could begin asking if there was anything that would differentiate them,” said Daryl Seligman of Michigan State University, who led the new research. “By analyzing the reflectivity [of the surface of the dark comets, which is related to their composition] and the orbits, we found that our solar system contains two different types of dark comets.”
One type lurks in the outer solar system, in the realm of the gas and ice giants . The other group is located in the inner solar system, sharing orbits with Mercury , Venus , Earth and Mars . The outer dark comets are larger, with diameters hundreds of meters across or greater, while the inner dark comets are far smaller, measuring tens of meters across, or less.
The outer dark comets have more eccentric, i,.e. elliptical, orbits that are more like those of typical comets, whereas the inner dark comets have more circular orbits like those of the planets. Seligman noted that the outer dark comets have some orbital properties in common with Jupiter-family comets , which are comets that have wandered in from the outermost reaches of the solar system and settled into orbits around the sun that don’t extend much farther out than Jupiter.
The whys and wherefores, however, remain mysterious. How did dark comets come to be in these two locations? In the summer of 2024, Seligman’s team showed how the inner dark comets, at the very least, could have ended up on their current orbits if they were perturbed from their birth zone in the inner region of the asteroid belt.
Related: ‘Dark comets’ may have given Earth its water long ago
Then there’s the question of how much water ice dark comets contain. When the solar system formed 4.5 billion years ago, there was an invisible demarcation called the ” snow line .” Inside the snow line, which was just a little bit closer to the sun than where Jupiter is now (about 5 astronomical units — roughly 465 million miles, or 750 million kilometers), temperatures in the protoplanetary disk were too warm for ice to form, and water existed as a vapor or a liquid instead. Beyond the snow line, where the planets of the outer solar system are now, it was cold enough for water to freeze into ice.
So it would not be surprising if the outer dark comets contain ice beneath their surface. But the inner dark comets that seemingly formed inside the snow line must also contain ice, to allow them to outgas and generate thrust for the non-gravitational acceleration. The earlier work of Seligman’s team indicates that as many as 60% of near-Earth objects could be dark comets, which raises the possibility that dark comets impacting on Earth long ago are what brought water to our planet .
“Dark comets are a new potential source for having delivered the materials to Earth that were necessary for the development of life,” said Seligman. “The more we can learn about them, the better we can understand their role in our planet’s origin.”
Scientists hail ‘strongest evidence’ so far for life beyond our solar system
K2-18 b is nearly nine times as massive as the Earth and 2.6 times as large. It orbits in the habitable zone of its star, a cool red dwarf less than half the size of the sun. Astronomers claim to have detected the chemical fingerprints of two compounds that, on Earth, are only known to be produced by life. The discovery could bring the answer to the question of whether we are alone in the universe much closer to us. But others are more sceptical, with questions remaining about whether the overall conditions on K2- 18 b, are favourable to life and whether DMS and DMDS, which are largely produced by marine phytoplankton, can be reliably regarded as biosignatures. The results are reported with a “three-sigma” level of statistical significance (a 0.3% probability that they occurred by chance) although this falls short of the gold standard for discoveries in physics. The findings suggest concentrations of DMS, DMDS or both (their signatures overlap) could be thousands of times stronger than the levels on Earth.
Observations by the James Webb space telescope of a planet called K2-18 b appear to reveal the chemical fingerprints of two compounds that, on Earth, are only known to be produced by life.
Detection of the chemicals, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) would not amount to proof of alien biological activity, but could bring the answer to the question of whether we are alone in the universe much closer.
“This is the strongest evidence to date for a biological activity beyond the solar system,” said Prof Nikku Madhusudhan, an astrophysicist at the University of Cambridge who led the observations. “We are very cautious. We have to question ourselves both on whether the signal is real and what it means.”
He added: “Decades from now, we may look back at this point in time and recognise it was when the living universe came within reach. This could be the tipping point, where suddenly the fundamental question of whether we’re alone in the universe is one we’re capable of answering.”
Others are more sceptical, with questions remaining about whether the overall conditions on K2-18 b, are favourable to life and whether DMS and DMDS, which are largely produced by marine phytoplankton on Earth, can be reliably regarded as biosignatures.
K2-18 b, which sits in the Leo constellation, is nearly nine times as massive as the Earth and 2.6 times as large and orbits in the habitable zone of its star, a cool red dwarf less than half the size of the sun. When the Hubble space telescope appeared to spot water vapour in its atmosphere in 2019, scientists declared it “the most habitable known world” beyond the solar system.
The supposed water signal was shown to be methane in follow-up observations by Madhusudhan’s team in 2023. But, they argued, K2-18 b’s profile was consistent with a habitable world, covered in a vast, deep ocean – a view that remains contentious. More provocatively, the Cambridge team reported a tentative hint of DMS.
Planets beyond our solar system are too distant to photograph or reach with robotic spacecraft. But scientists can estimate their size, density and temperature and probe their chemical makeup by tracking the exoplanet as it passes across the face of its host star and measuring starlight that has been filtered through its atmosphere. In the latest observations, wavelengths that are absorbed by DMS and DMDS, were seen to suddenly drop off as K2-18 b wandered in front of the red dwarf.
“The signal came through strong and clear,” said Madhusudhan. “If we can detect these molecules on habitable planets, this is the first time we’ve been able to do that as a species … it’s mind-boggling that this is possible.”
The findings, published in The Astrophysical Journal Letters, suggest concentrations of DMS, DMDS or both (their signatures overlap) thousands of times stronger than the levels on Earth. The results are reported with a “three-sigma” level of statistical significance (a 0.3% probability that they occurred by chance) although this falls short of the gold standard for discoveries in physics.
“There may be processes that we don’t know about that are producing these molecules,” Madhusudhan said. “But I don’t think there is any known process that can explain this without biology.”
A challenge in identifying potential other processes is that the conditions on K2-18 b remain disputed. While the Cambridge team favour an ocean scenario, others say the data is suggestive of a gas planet or one with oceans made of magma, not water.
There is a question of whether DMS could have been brought to the planet by comets – this would require an intensity of bombardment that seems improbable – or produced in hydrothermal vents, volcanoes or lightning storms through exotic chemical processes.
“Life is one of the options, but it’s one among many,” said Dr Nora Hänni, a chemist at the Physics Institute of the University of Berne, whose research revealed that DMS was present on an icy, lifeless comet. “We would have to strictly rule out all the other options before claiming life.”
Others say that measuring planetary atmospheres may never yield a smoking gun for life. “It’s under-appreciated in the field, but technosignatures, such as an intercepted message from an advanced civilisation, could be better smoking guns, despite the unlikelihood of finding such a signal,” said Dr Caroline Morley, an astrophysicist at the University of Texas, Austin, adding that the findings were, nonetheless, an important advance.
Dr Jo Barstow, a planetary scientist at the Open University, also viewed the detection as significant, but said: “My scepticism dial for any claim relating to evidence of life is permanently turned up to 11, not because I don’t think that other life is out there, but because I feel that for such a profound and significant discovery the burden of proof must be very, very high. I don’t think this latest work crosses that threshold.”
At 120 light years away, there is no prospect of resolving the debate through closeup observations, but Madhusudhan notes that this has not been a barrier to the discovery of black holes or other cosmic phenomena.
“In astronomy, the question is never about going there,” he said. “We’re trying to establish if the laws of biology are universal in nature. I don’t see it as: ‘We have to go and swim in the water to catch the fish.’”
Is there really alien life on this exoplanet? We asked 10 experts.
Scientists say they’ve detected a gas called dimethyl sulfide (DMS) in the atmosphere of an exoplanet called K2-18b. On Earth, DMS is mostly made by microscopic phytoplankton. On other planets, it could be what’s called a biosignature—a sign of life. In 2020, scientists claimed to have found signs of life on Venus. The claim was swiftly challenged and, years later, is still mired in controversy. Now, another stinky gas has sparked its own alien life debate—this time, for an ex planetet.. National Geographic got in touch with ten independent experts to find out what to make of this biosignatures claim. The takeaway: It’s an exciting discovery, perhaps even an important step on the way to discovering alien life one day. We did not just find aliens. We found a planet with an ocean teeming with life. It’s called a Hycean world, and it could have temperate surface oceans hospitable for life.
Researchers announced on April 16 that they’d used data from the James Webb Space Telescope (JWST) to detect a gas called dimethyl sulfide (DMS) in the atmosphere of an exoplanet called K2-18b, which orbits in its alien star’s habitable zone. On Earth, DMS is mostly made by microscopic phytoplankton. On other planets, it could be what’s called a biosignature—a sign of life.
Cambridge University, which hosts several of the researchers involved in the detection, was quick to promote the finding as the “strongest hints yet of biological activity outside the solar system.” Some media outlets trumpeted the DMS as a likely sign of life. But scientists who weren’t involved in the discovery aren’t as euphoric.
Advertisement Advertisement
Advertisement Advertisement
“I’m pretty skeptical of this claim, and I wish the press coverage better reflected the skepticism of the astronomical and astrobiological community,” wrote astrobiologist Joshua Krissansen-Totton of the University of Washington in an email.
For Clara Sousa-Silva, an astrochemist at Bard College who was involved in the 2020 Venus biosignature debacle, the situation is disappointingly familiar. “We did not learn enough from the ‘phosphine on Venus’ drama,” she says.
National Geographic got in touch with ten independent experts to find out what to make of this biosignature claim. (Not all are quoted below, but their views are represented.) The takeaway: It’s an exciting discovery, perhaps even an important step on the way to discovering alien life one day. Emphasis on “one day.” We did not just find aliens.
Here’s what you need to know about DMS on K2-18b.
What are the researchers claiming?
If you follow exoplanet news, you might be feeling a bit of déjà vu. In 2023, the same research team led by Cambridge astrophysicist Nikku Madhusudhan published JWST observations hinting at DMS on K2-18b.
Advertisement Advertisement
Advertisement Advertisement
Based on the same JWST data, the researchers also concluded that K2-18b was a type of habitable planet called a “Hycean” world. Madhusudhan and his colleagues coined the term in 2021 to describe a group of hypothetical planets bigger than Earth, smaller than Neptune, mostly made of water, and wreathed in thick veils of hydrogen and helium. Under the right conditions, they could have temperate surface oceans hospitable for life.
The DMS detection from 2023 fell short of the typical statistical standards for discoveries in astronomy. This new study, published in the Astrophysical Journal Letters, is a follow-up using an instrument on JWST that’s sensitive to light at different wavelengths than the original study.
While the last DMS detection was weaker than tentative, this one appears to be much stronger. Madhusudhan and his colleagues claim that their detection of DMS (and/or a similar molecule called dimethyl disulfide or DMDS) reaches a “three sigma” level of significance. That’s statistical jargon meaning there’s less than a 0.3 percent chance that the DMS detection was made by chance—still lower than the gold standard five sigma cutoff for statistical significance, but far more convincing than before.
“Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have,” Madhusudhan said in Cambridge’s press release.
Is the dimethyl sulfide even there?
Other scientists aren’t as sanguine. Some are skeptical that the DMS (or DMDS) is even there at all.
Advertisement Advertisement
Advertisement Advertisement
“It’s really interesting, a great showcase of the capabilities of JWST,” astronomer Laura Kreidberg of the Max Planck Institute for Astronomy said in a voice memo. “But, yeah, I wouldn’t bet my house on it.”
Scientists can use JWST to identify gases in exoplanet atmospheres via chemical fingerprints in starlight that has filtered through the planets’ atmospheres. Those chemical fingerprints show up as wiggles in graphs of the starlight’s intensity versus its wavelength. The new study tried to match these spectral wiggles to 20 molecules. That’s “more molecules than astronomers often do, it’s just astronomers don’t often claim aliens,” says Sousa-Silva. Most of those molecules aren’t structurally similar to DMS and DMDS, either, she notes, so it wasn’t exactly a targeted screen of possible false-positives.
Another researcher, astronomer Ryan MacDonald at the University of Michigan went further, criticizing the three sigma claim as “statistical hacking” on Bluesky.
Kreidberg is more forgiving. “I think that the discovery team did a great job, really careful work with the data. But as someone in this business myself, I can say that it is just really hard.”
Advertisement Advertisement
Advertisement Advertisement
Already, researchers have formally challenged the biosignature claim. In a preliminary study posted to arXiv.org on April 22, astrophysicist Jake Taylor of the University of Oxford found no strong evidence for DMS and/or DMDS in the new JWST data.
Is K2-18b even habitable?
Though K2-18b orbits in its star’s habitable zone, it is not a second Earth. At 2.6 times the radius and 8.6 times the mass of our planet, it is a mysterious and alien world—one that might not even be habitable.
When an independent team recently reanalyzed the Cambridge team’s 2023 observations of K2-18b, they found no evidence of DMS, nor of carbon dioxide—a blow to the Hycean world scenario, which predicted plenty of carbon dioxide. An earlier study claimed that K2-18b is most likely an inhospitable gassy ball with no surface whatsoever. Another team has suggested an even less hospitable alternative: The planet could have an ocean not of water, but of magma.
Madhusudhan points out that the analysis reporting no carbon dioxide on K2-18b has not yet been peer-reviewed. “There are open questions, but they don’t preclude habitability,” he says. “The evidence for CO 2 is certainly there.”
Advertisement Advertisement
Advertisement Advertisement
Even if K2-18b is a Hycean world, that doesn’t mean it is habitable. Without a reflective deck of clouds, the planet’s ocean would broil beneath its hydrogen blanket. That’s the likely fate of any ocean that might exist on K2-18b, at least according to a study posted last week.
“The simplest explanation of this planet is a very thick gas-giant atmosphere with no habitable surface,” says exoplanet scientist Nick Wogan of NASA Ames. “There are so many challenges with making a habitable (or inhabited) K2-18b work.”
If the dimethyl sulfide is there, was it made by life?
Still, let’s say scientists confirm the DMS signal, and K2-18b turns out to be a habitable Hycean world. You still might want to hold off on popping the “we found aliens” champagne.
Until scientists can rule out abiotic explanations—ones that don’t involve living things—for DMS and/or DMDS, these gases won’t be true biosignatures for K2-18b. And as Harrison Smith, an astrobiologist at the Earth-Life Science Institute in Japan, and his colleague Cole Mathis at Arizona State University argued in a 2023 essay, ruling out false positives for exoplanets is very hard.
Advertisement Advertisement
Advertisement Advertisement
“At least Venus is a planet we know. We know what it looks like, and what the environment is like,” says Sousa-Silva. Without knowing what K2-18b’s geochemistry and atmosphere are really like, scientists can’t confidently exclude the possibility that alien chemistry, not alien life, is the source of the DMS.
And we already know that nature can produce DMS without life. Last year, chemist Nora Hänni at the University of Bern and her colleagues found DMS on comet 67P—not exactly a habitable world. Other researchers have found it in interstellar space. And last year, chemist Eleanor Browne of the University of Colorado, Boulder and her colleagues showed that DMS can be produced in light-fueled chemical reactions in lab experiments with synthetic atmospheres.
“There’s no reason to understand [DMS] as a unique consequence of life,” says Mathis. “I just, for the life of me, cannot figure out exactly what the argument is about: why they think this could even potentially be indicative of life, given that we’ve seen abiotic sources.”
The study authors acknowledge some of these challenges. Madhusudhan says that neither comets nor interstellar material are feasible sources of the high concentrations of DMS and DMDS his team detected. But finding DMS in unexpected, dead environments shows that we still have a lot to learn about how it forms.
Embracing uncertainty
Other uncertainties haunt the detection. We don’t know how life began on Earth, so we can’t know if conditions on K2-18b — even if they’d be hospitable for earthlings — could have got life started in the first place. And even if life did evolve there, who’s to say that it’d produce DMS — and if it does produce DMS, why haven’t scientists spotted other biosignature gases?
Advertisement Advertisement
Advertisement Advertisement
Still, despite its many, many caveats, most researchers we spoke with agree that there’s reason to celebrate this new study of K2-18b. “It’s really an achievement. Thirty years ago, we didn’t even know that there are exoplanets,” says Hänni.
Peter Vickers, a philosopher of science at Durham University who’s studied life detection claims, was initially skeptical. “But then the more I looked at it, the more I thought that it actually is quite significant and shouldn’t be underplayed either,” he says.
For Madhusudhan’s part, he doesn’t think caution and excitement are mutually exclusive. Even a sliver of evidence for alien life is a “transformational achievement” he says, but there’s a big step from there to a true life detection claim. “We need to recognize both: the achievement and the caution.”
If we do ever find life beyond our solar system, it won’t happen all at once. We’ll slide slowly into certainty, pushed along by findings like this one—hints that there’s something more to discover if only we’d look closer. And this result is, without a doubt, an invitation to look closer at K2-18b. If we find life there, on one of the first potentially habitable planets we’ve inspected closely, says Vickers, we’ll have to assume life is common everywhere; if life is rare, the odds of just stumbling upon the right planet are astronomically low.
Advertisement Advertisement
Advertisement Advertisement
“We’re still only at the question asking stage, but it’s amazing that we can ask this question,” says astrobiologist Michael Wong of Carnegie Science. “What a lucky time to be alive.”
Editor’s note: This story was updated on April 19, 2025, to clarify the timing of efforts to reanalyze the Cambridge team’s 2023 observations and model the composition of K2-18b. It was updated again on May 1, 2025, to include the first reanalysis of the new JWST data.
The best sci-fi TV shows of all time, according to New Scientist
We asked our writers to pick their favourite science fiction television series. Here are the results, from Battlestar Galactica to Futurama. The New Scientist team found picking their favourite sci-fi series a tricky task – not everyone could narrow it down to one. We hope that our selection contains something for everyone, no matter what kind of sci-Fi fan you are. The X-Files, The Expanse, Doctor Who, Black Mirror and The Walking Dead are all included in the list. The list is presented in no particular order, and we hope it will be of interest to all sci-fiction fans, not just those with a love of the genre. The full list is available on the New Scientist website and can be downloaded for free from the website’s home page: http://www.newscientist.co.uk/sci-fi/top-10-favourites-science-fiction-television-shows-to-be-viewed-in-the-coming-years.
Gillian Anderson (left) and David Duchovny as agents Scully and Mulder in The X-Files AJ Pics/Alamy
Television hasn’t always been kind to science fiction, with smaller budgets to throw at special effects and epic, universe-spanning narratives getting cancelled before their time. But despite all the obstacles, countless series have proved that long-form storytelling on the small screen is the perfect way to explore the complex ideas and philosophies that make this genre so compelling.
With so much gold to choose from, the New Scientist team found picking their favourite sci-fi series a tricky task – not everyone could narrow it down to one. Though this is far from a definitive list (and is presented in no particular order), we hope that our selection contains something for everyone, no matter what kind of sci-fi fan you are.
Rebooted from an ill-fated 1978 series, Battlestar Galactica begins with a nuclear holocaust and humanity’s remnants crowding aboard battered spaceships to flee from sentient machines. But its most compelling moments involve the survivors struggling to balance societal and ethical norms against the cold calculus of survival. Jeremy Hsu
Advertisement
Katee Sackhoff as Kara “Starbuck” Thrace in Battlestar Galactica Cinematic/Alamy
The Leftovers isn’t just the best sci-fi series I have seen, it’s perhaps the greatest TV show ever made. Big claim, I know. The premise is weird: what if one day, out of nowhere, 2 per cent of the population disappeared? Don’t expect answers to why this happened – the series doesn’t offer any. Instead, it explores the gritty fallout of so much inexplicable grief and loss. Chelsea Whyte
My family weren’t into Doctor Who, so this show was, I think, my introduction to science fiction (if you count time travel as science fiction, which I most definitely do). It follows physicist Sam Beckett (Scott Bakula), who has invented a way to travel through time, although it’s not quite what he expected. Sam has vanished from his own reality, but his consciousness leaps into the bodies of other people, whose lives he must sort out before he can move on – and hopefully return home. The series was revived in 2022 – and when I get a minute to myself that isn’t filled with children or books or the need to sleep, I shall be watching it. Alison Flood
Two parts sci-fi, one part noir, the richly detailed universe of The Expanse has drawn me in like no other. Set in a future where humanity has colonised the solar system, it follows the crew of a deep-space ice hauler and a hard-boiled detective investigating the disappearance of a wealthy heiress. Before long, they are embroiled in conspiracies and a rebellion by the exploited, asteroid-dwelling Belters. Long live the Outer Planets Alliance! Bethan Ackerley
Black Mirror operates in a strange twilight zone of science fiction, not quite fanciful enough to feel truly invented, but a little too futuristic to feel like a real-world drama. Each episode dives into the way technology is warping human experience, hopping genres from romcom to slasher horror. The earliest series are the most arresting – the first episode, featuring the UK Prime Minister and a pig, will be burned into your brain – but throughout Black Mirror is thought-provoking, disturbing and often darkly funny. Madeleine Cuff
How many stories start with someone opening a door and stepping into the unknown? The joy of Doctor Who, and one of the two reasons for its longevity, is that the titular Doctor’s spacecraft is a portal to anywhere in time and space. You can set a story in Victorian London or a billion years in the future. The other reason why the show has lasted over 60 years is that the Doctor can regenerate into a new body – convenient when you want to cast a new lead. Rowan Hooper
I began watching The X-Files at around 9 years old – far too young! I thought Mulder was the epitome of cool, I wanted to believe, and I was fascinated and terrified by the monsters he and Scully encountered each week. Revisiting the series as an adult, I identified more with the sceptical Scully and was drawn to the long-running narrative of an alien conspiracy. It is this structure of weaving standalone plots with ongoing stories that makes The X-Files so good. Let’s just pretend the 2010s revival never happened. Jacob Aron
The One Amigo episode from Futurama Disney
Set in New New York at the turn of the 31st century, this animated series is, in essence, your classic workplace sitcom, with all the main characters working at interplanetary delivery company Planet Express (including Philip J. Fry, who was cryogenically frozen in 1999 and wakes up 1000 years later). Futurama has an absurdly high gags-per-minute ratio, but there are also deeply poignant moments – even the mere thought of Fry’s dog makes me sob – and frequent, satisfying homages to science fiction. Tim Boddy
Imagine Han Solo from Star Wars walking into a Wild West saloon. A mash-up of Westerns and sci-fi, Firefly sees a crew of lovable misfits on the spacecraft Serenity trying to survive and make a difference in a space empire ruled by the Alliance. The series has become a cult classic thanks to its idiosyncratic characters, compelling cast, inventive storylines and snappy dialogue. Chris Simms
New Scientist book club Love reading? Come and join our friendly group of fellow book lovers. Every six weeks, we delve into an exciting new title, with members given free access to extracts from our books, articles from our authors and video interviews. Sign up
At first glance, Fringe may seem like a successor to The X-Files: it features a somewhat antagonistic duo of oddball investigators and quickly plunges into both the supernatural and the personal. But it is so much more than that. Where The X-Files had aliens and government conspiracies, Fringe has parallel universes, family secrets, psychedelics and sensory deprivation – plus an incredibly strong cast of supporting characters. Expect Leonard Nimoy as a multiversal villain, doppelgangers and men-turned-giant-porcupines. Karmela Padavic-Callaghan
I’m reluctant to admit that sci-fi isn’t my go-to choice of entertainment – tales of robots and aliens don’t really do it for me. But Outlander offers an alternative take on the genre, with plenty of romance and a swashbuckling heroine. It follows Claire Beauchamp, who accidentally travels back in time from 1945 to 1743. Once she has accepted her fate (and met the love of her life, Jamie), Claire, a nurse, bewilders her contemporaries with her 20th-century knowledge of anatomy and pathogens – not to mention her feminist attitude. Alexandra Thompson
The Star Wars franchise started as an uncomplicated space opera: the Empire is evil because its agents look like fascists; the rebels are good because they aren’t that. But recent instalments have gone a long way in complicating that narrative. Andor explores what an “ordered” space empire would look like – colonialist, banal, dehumanising – and why those conditions make heroes out of thieves. Linda Rodriguez-McRobbie
There is something about Altered Carbon that is awful and depressing, but also incredibly appealing. Who wouldn’t want to be able to try out a smorgasbord of different bodies, or “sleeves” as they are called in the show? Epic cities, gross inequality, affable AIs and a questionable storyline – this cyberpunk series has it all! Finn Grant
I am terrible at watching telly in the evenings after work/children/life are in the bag for the day – I generally just fall asleep. Not when it comes to the adventures of Rick (Andrew Lincoln), Michonne (Danai Gurira) and their ragtag crew, though. I have watched every episode of The Walking Dead, from Rick’s awakening in hospital to discover a world ravaged by a virus that has turned everyone into “walkers” to the various terrible communities they keep stumbling across. It’s shocking, well-acted and, particularly in the earlier series, full of surprises. Alison Flood
The Star Trek crew in 1966 Album/Alamy
The original Star Trek is an aspirational model for a society led by science, one with true equality and peaceful exploration. That’s a pretty cathartic means of escapism in today’s tumultuous world, perhaps even more so than it would have been in the 1960s. It’s a great show to dip in and out of, and the over-the-top Technicolor, terrible special effects and wooden acting only add to its appeal. The series spawned a bewildering array of spin-offs of varying quality, but in my opinion you can’t beat the original. Matthew Sparkes
How different would your life be if you had made different decisions at key points? And what would you do if you could visit the other multiverses spawned at these points, with different yous? That’s the intriguing premise of Dark Matter, adapted for TV by Blake Crouch from his own book. The first few episodes can be a little slow at times, but it gets better and better after that. Michael Le Page
Recency bias be damned: despite only debuting in 2022, Severance has already earned its place among the greatest sci-fi TV of all time. Imagine if you could separate your memories of work from the rest of your life. At first, outsourcing the daily grind may seem like a no-brainer – but what horrors might your body unknowingly experience at the office, and what misery might the alternate version of yourself endure? Bethan Ackerley
Avi Loeb’s search for alien life and the conflict it has sparked : NPR
Avi Loeb is a tenured professor at Harvard University. He has published over a thousand scientific papers on black holes and how the first stars and galaxies formed. But exploring the possibility of extraterrestrial life has created a huge rift between him and many of his colleagues. They are questioning whether his ideas should even exist within their scientific community, just as Avi wonders whether we humans coexist with other life forms. He says, “I’m just a boy, I’m curious and I’m a farm boy, and I wonder what’s out there in the universe” It’s the TED Radio Hour from NPR. Today on the show: Coexistence, the search for aliens in interstellar space, and the future of our species. The show is presented by Manoush Zomorodi, and it’s on CNN.com and the TEDRadio Hour on NPR 1, 2, 3, 4, 5 and 6 p.m. ET. For more, go to ted.com/RadioHour.
MANOUSH ZOMORODI, HOST:
It’s the TED Radio Hour from NPR.
AVI LOEB: One, two, three, four, five. Can you hear me?
ZOMORODI: I’m Manoush Zomorodi.
Hi, Avi.
LOEB: Hi. Good to speak with you.
ZOMORODI: And you. And you.
Today on the show – Coexistence…
It sounds like it’s clicking in and out a little bit.
LOEB: OK, let me see. Maybe the connection here – let me just…
ZOMORODI: …With other humans, animals and whatever is out there in space.
Would you mind just introducing yourself? Tell us your name and what you do.
LOEB: My name is Avi Loeb. And I’m – I have the privilege of being a scientist, meaning that I can follow my childhood curiosity without pretending to be the adult in the room.
ZOMORODI: (Laughter).
(SOUNDBITE OF MUSIC)
ZOMORODI: If you know a lot about astrophysics, then you know who Avi Loeb is. For the past four decades, he has been a leader in the field.
LOEB: I’m a tenured professor at Harvard University, and then I was also chair of the astronomy department at Harvard for nine years.
ZOMORODI: Avi has published over a thousand scientific papers on black holes and how the first stars and galaxies formed.
LOEB: I’ve been the director of the Institute for Theory and Computation at Harvard. I was the founding director of Harvard’s Black Hole Initiative.
ZOMORODI: He’s written nine books.
LOEB: I chaired the Board of Physics and Astronomy of the National Academies. I chaired the advisory board for the Breakthrough Starshot initiative, which is the first…
ZOMORODI: Yeah, he’s a big deal. But over the last decade or so, he has put that reputation in jeopardy by searching for something else in the cosmos.
LOEB: I think it will be the biggest discovery in science ever made in terms of its impact on the future of humanity.
(SOUNDBITE OF MUSIC)
ZOMORODI: Signs of life.
LOEB: We are searching for artifacts that may have been manufactured by extraterrestrial civilizations.
ZOMORODI: That’s right. Avi is looking for aliens.
LOEB: Yes. That’s my latest hobby (laughter).
ZOMORODI: But why? Why go on a quest that, to some of his fellow scientists, sounds ridiculous?
LOEB: You know, one reason I search for higher intelligence in interstellar space is because I don’t often find it here on Earth.
ZOMORODI: (Laughter).
As far as Avi is concerned, the scientific method requires us to ask questions and seek answers. So why is he doing this? He says, why not? But exploring the possibility of extraterrestrial life has created a huge rift between him and many of his colleagues. They are questioning whether his ideas should even exist within their scientific community, just as Avi wonders whether we humans coexist with other life forms.
(SOUNDBITE OF MUSIC)
LOEB: Space is vast. It’s measured in tens of thousands of light years just within the Milky Way galaxy alone. So to imagine, you know, there are other beings like us on similar rocks far away. It’s very natural.
ZOMORODI: I mean, you’re right. Everyone – we love to watch movies about other beings that might be out there in the universe. We love to think about this idea that we might not be alone. It is fascinating to people. And you are saying, well, you know, let’s use the science to see if there is a way that it might be sure.
LOEB: Exactly. Let’s use the scientific method, which is, basically, let’s not imagine anything the way Hollywood does. Let’s not assume anything. To make progress, we need to collect data. And, you know, new knowledge does not fall into our lap. And so you have to put effort, money, time in order to design instruments that will detect those very challenging signals.
ZOMORODI: Here’s Avi Loeb on the TED stage.
(SOUNDBITE OF TED TALK)
LOEB: I’m just a curious farm boy, and I wonder about the world around me. And I hate to behave like the adults in the room because they often pretend to know more than we actually know, and that bothered me since I was a young kid. And so I decided to become a scientist and answer the questions based on evidence, not based on prejudice. And for 70 years, we’ve been searching for radio signals. This is equivalent to staying at home and waiting for a phone call that may never come because nobody cares that we are lonely. A much better approach is to check if there is any object in our backyard that may have arrived from a neighbor’s yard, like a tennis ball that may tell us that the neighbor plays tennis. People often say extraordinary claims require extraordinary evidence, but they are not seeking the evidence. So let’s just look around.
(SOUNDBITE OF MUSIC)
ZOMORODI: To understand why Avi began his search for alien life, we need to go back to 2017 when scientists spotted a strange object in the sky.
LOEB: This was an object called ‘Oumuamua, which means a scout in the Hawaiian language. It was discovered by telescope named the Pan-STARRS in Hawaii, on Mount Haleakala.
ZOMORODI: ‘Oumuamua was unlike anything Avi and other astrophysicists had ever seen before. And it raised a lot of questions, namely what was it, and where did it come from?
LOEB: At first, you know, we just knew that this is an object from outside the solar system because it moved too fast to be bound by gravity to the sun. And so it was clear beyond any doubt that it came from outside the solar system. So everyone assumed that it must be an asteroid or a comet, the type of objects we find within the solar system – rocks or icy rocks. But there was no cometary tail.
(SOUNDBITE OF MUSIC)
ZOMORODI: Even more perplexing was the way that the object moved through space.
LOEB: The object showed a push away from the sun by some mysterious force. And so it’s as if there was something pushing it away from the sun. It’s a nongravitational acceleration, but there was no cometary evaporation, no gas or dust around it. So the question was, what is exerting this force on the object?
ZOMORODI: Scientists looked for an explanation, any explanation.
LOEB: You know, some of my colleagues argued, maybe you can explain these anomalies by imagining a hydrogen iceberg, a chunk of frozen hydrogen, which so then someone else said, well, maybe it’s a nitrogen iceberg. And then someone else said, well, maybe it’s a dust bunny.
ZOMORODI: But Avi wasn’t convinced. He suggested another hypothesis, that perhaps ‘Oumuamua was not naturally occurring. Perhaps it was produced by something or someone from another planet. Perhaps it was alien technology.
LOEB: And just the suggestion that it might be artificial got me into trouble because I was not supposed to consider that possibility. How dare you even think about that? It’s a rock of a type that we’ve never seen before, period.
ZOMORODI: Avi published a paper about his hypothesis, which launched a slew of criticism from his colleagues who said that he was leaping to the conclusion that ‘Oumuamua was proof of aliens without exhausting every other possibility.
LOEB: All of the alternative explanations had issues. And I just said, let’s keep the artificial origin on the table because we are producing space trash. Another civilization might have done the same.
ZOMORODI: Then, in 2023, two scientists published a paper in Nature with a new explanation for ‘Oumuamua, that it was simply a comet with no tail. Scientists now call this a dark comet, an object that moves like a comet but looks like an asteroid. The explanation does not satisfy Avi.
LOEB: Because the only way you define a comet is by detecting its cometary tail. That’s what a comet is. So if you say that an elephant is an unstriped zebra, you know, that sounds strange because it’s not the same animal. OK? And so my point is, when you don’t see a cometary tail, don’t call it a comet.
ZOMORODI: In 2024, research was published on the discovery of more dark comets, largely settling the issue for the scientific community.
(SOUNDBITE OF MUSIC)
ZOMORODI: By now, most researchers have moved on from the ‘Oumuamua debate, but the public has not. Ever since his suggestion that ‘Oumuamua could be a sign of alien life, Avi has gotten more attention and funding from people outside the world of astrophysics than ever before. He may have lost favor with his colleagues, but he has gained a whole new audience.
LOEB: Yeah, so on the one hand, the public really was extremely fascinated by this possibility, and I got a huge amount of attention from the media, something that I was not familiar with before. And I was also contacted by a literary agent to write a book, which ended up being “Extraterrestrial,” became bestseller. And I participated in about 3,500 podcast interviews. Netflix is producing a documentary.
ZOMORODI: Thanks to all this attention, in 2021, Avi co-founded the Galileo Project at Harvard, a research program dedicated to searching for alien technology on and near Earth. Avi and his team have received millions of dollars in private funding from a long list of uberwealthy donors.
(SOUNDBITE OF MUSIC)
LOEB: We built an observatory at Harvard University. It’s a unique observatory. Usually, astronomical observatories are focusing on a small portion of the sky and looking at very distant sources. But here we are looking at the entire sky all the time and, in particular, searching for objects near Earth that are just overhead. And we are using infrared cameras, optical cameras, radio sensors, audio sensors, and analyzing the data with machine learning software, using state-of-the-art algorithms to figure out if there are any objects that are not familiar. I’m not trying to imagine what might be out there. I’m just saying we know about birds. We know about airplanes, leaves, clouds, satellites, balloons, drones. These are things we know about. And is there anything else? And if we find an object that is maneuvering in ways that does not mimic the flight characteristics of known objects, we will write a paper about it and share it with the scientific community. And for me, having more data is really bliss because once you have a lot of data, it will become clear whether we’re dealing with a rock of a type that we’ve never seen before, or maybe some artificial object, and at some point, it would be impossible to ignore it.
(SOUNDBITE OF MUSIC)
ZOMORODI: There are probably going to be people listening who are saying, why – and these are scientists on Earth right now who would say, why are you giving Avi Loeb the mic? You have become a bit of a pariah in your field. I want to quote one astrophysicist, Steve Desch, who said, people are sick of hearing about Avi Loeb’s wild claims. It’s polluting good science, conflating the good science we do with this ridiculous sensationalism, and sucking all the oxygen out of the room. There’s a lot of ire towards you, a field that embraced you for the longest time. And now what’s it like having them call you names?
LOEB: Yeah, I really don’t like that. But one thing I learned is that, you know, if you don’t want to get dirty, don’t mud wrestle. So I don’t respond to those. I am still the director of the Institute for Theory and Computation. I work with students. I work with postdocs. I just gave a lecture at the Black Hole Initiative about primordial black holes. So I continue to work on other subjects as well, and the people who know me, you know, are very supportive because they know that I’m doing it not out of any other reason than advocating for something I believe in that should be studied.
And, you know, I borrowed the approach from the research on dark matter that I worked on early on in my career. You know, we don’t know what 85% of the matter in the universe is. So billions of dollars are spent on the searches for dark matter. Specific types of particles that were proposed by theories like myself were very much rewarded by attention and so forth. So I have that experience. And for me, it’s no different. But for some reason, this particular subject is making some people very upset. And those are people who are upset about the public attention that I’m getting.
(SOUNDBITE OF MUSIC)
LOEB: You know, when I gave my class at Harvard, in the opening lecture I asked the students, what is the strongest force in academia? Is it gravity? Is it electromagnetism? They were quiet, and then I answered the question myself. I said, no, it’s jealousy.
ZOMORODI: Ha. Can I ask you, how would you know? You’ve given us several examples of all the data and specimens that you’re collecting and sort of sifting through all of this. How will you know for sure? What would be the moment where you could tell the rest of the world, yes, we are not alone. There – we are coexisting with an – something else that is alive.
LOEB: Well, that’s relatively straightforward if you have good enough data. For example, if we had an image of an interstellar object and you see bolts and screws and you see that it looks like a technological object, there is no doubt that it’s not a rock. That would be clear evidence.
ZOMORODI: Let’s say this did happen. How would it change things for us? What – you must have imagined this scenario in your mind.
LOEB: Yes. I think it will change our perspective because, you know, when you find a partner, it changes the meaning of your existence. We know that from our personal lives. And here, I’m just talking about finding a partner in the global scheme of the cosmos. These are all the Earth-sun systems. You know, there are a hundred billions of them in the Milky Way galaxy alone and perhaps a trillion galaxies in the observable volume of the universe at large. We see so many houses like our own. And to me, it’s very natural to imagine that there are residents that we can learn from. So just paying attention to our cosmic neighborhood, you know, will allow us to mature and realize that what we usually care about is not as important as the bigger scheme of things. And we could do better by paying attention to our neighbors.
(SOUNDBITE OF TED TALK)
LOEB: When I look up at the sky at night, I see a hundred billion stars of the Milky Way galaxy. They look like lights in cabins of a giant spaceship – the Milky Way – sailing through space. And I wonder if there are other passengers in those cabins. There are a hundred billion of them, comparable to the number of people who ever lived on Earth. It would be arrogant to think otherwise – that we are alone, that we are unique and special, especially if you read the news every day. We are not the pinnacle of creation.
(LAUGHTER)
LOEB: There is room for improvement.
(LAUGHTER)
LOEB: And so the next Copernican revolution would be that we are not at the intellectual center of the universe. Not only that we are not at the physical center of the universe, but actually, you know, we arrived to the play relatively late. We are not at the center of stage. The play is not about us. We should be modest. We keep thinking that it’s about us, but it’s not. And we better find other actors that will tell us what the play is about.
ZOMORODI: That was astrophysicist Avi Loeb. He is a professor of science at Harvard University’s Department of Astronomy. His latest book is called “Interstellar: The Search For Extraterrestrial Life And Our Future In The Stars.” You can see his full talk at ted.com. On the show today – Coexistence. I’m Manoush Zomorodi, and you’re listening to the TED Radio Hour from NPR. Stay with us.
Copyright © 2025 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.
Accuracy and availability of NPR transcripts may vary. Transcript text may be revised to correct errors or match updates to audio. Audio on npr.org may be edited after its original broadcast or publication. The authoritative record of NPR’s programming is the audio record.
Source: https://www.chron.com/news/space/article/interstellar-object-alien-comet-20780216.php